Children are at risk of dangerous levels of air pollution in cars because exposure to toxic air is often far higher inside than outside vehicles. Prof Sir David King, a former UK Government chief scientific adviser, writing for the Guardian, says walking or cycling to school would be much better for children’s health. The warning comes as the UK government faces a third legal defeat for failing to tackle the country’s illegal levels of air pollution. Air pollution is known to damage children’s developing lungs but recent research also indicates it harms children’s ability to learn at school and may damage their DNA.

“Children sitting in the backseat of vehicles are likely to be exposed to dangerous levels [of air pollution],” said King. “You may be driving a cleaner vehicle but your children are sitting in a box collecting toxic gases from all the vehicles around you.” King, who now advises the British Lung Foundation says “It’s been shown that the health benefits of walking and cycling far outweigh the costs of breathing in pollution. If more drivers knew the damage they could be doing to their children, I think they’d think twice about getting in the car.”

A range of experiments, some as far back as 2001, have shown that drivers inside vehicles are exposed to far higher levels of air pollution than those walking or cycling along the same urban routes. Prof Stephen Holgate, an asthma expert at Southampton University and chair of the Royal College of Physicians working party on air pollution, said there was enough evidence to tell parents that walking and cycling exposes their children to less air pollution than driving and increase physical exercise. Children are more vulnerable than adults, because air pollution can stunt the growing of their lungs and it increases the risk of sensitisation which can lead to asthma and other respiratory conditions. “There are multiple benefits to be gained. But parents are confused at the moment because they think there is less pollution in cars than outside, which is not the case.”

The environmental law firm ClientEarth has defeated the ministers twice in the courts over the adequacy of government air quality plans. Ministers’ latest proposals were published on 5 May but were widely condemned as inadequate, and ClientEarth is now suing the UK government a third time.

“Air pollution hasn’t been taken seriously,” said Holgate. “There is a very strange situation where the government has to make laws by being taken to court repeatedly. In my view it is really quite appalling that we haven’t started to deal with this properly and put children’s and adults’ health first.”